Mainly due to frontman Jónsi Birgisson’s focus on solo projects in the past few years, there’s been little insight, let alone new material, surfacing from the Icelandic dream-pop experimentalists. Sensing this, who knows, Sigur Ros has uploaded to its SoundCloud a slew of new unreleased tracks, like demos, alternate versions or rare lives, which never made the final studio draft for one reason or another, but which are now up on the web for your…